The present invention relates to liquid rheostats used in liquid pumping systems, and more particularly to a novel method and apparatus for regulating electrolyte solution level in a liquid rheostat.
Liquid rheostats have been advantageously employed in controlling motor speed of a primary pump used for pumping liquid, such as sewage, from a sump or well. As is conventional, a liquid rheostat may include an electrode compartment which is mounted adjacent an electrolyte solution reservoir, and a circulating pump is used to circulate the electrolyte solution from the reservoir into the compartment. Extending from the bottom of the electrode compartment is a conduit for returning the electrolyte solution to the reservoir. Typically, a pneumatically-operated valve is used for regulating the amount of electrolyte solution being returned. The valve may be controlled by an electrical signal which originates from a sensor immersed in the liquid in the well. It can be seen that the electrical signal must be converted to a pneumatic signal for operating the valve.
Thus, depending upon liquid level in the well, the regulating valve is actuated to permit selected amounts of electrolyte solution to be returned into the reservoir. The circulating pump is driven by a constant speed electric motor thereby resulting in a constant recirculating rate of electrolyte solution. The electrolyte solution level in the electrode compartment may be adjusted only by means of operation of the regulating valve.
Generally, regulating valves, as described above, are pneumatically actuated while the sensors immersed in the well may directly sense pressure or level and produce an electrical signal. Conversion of the electrical signal into a pneumatic signal requires expensive controllers which may need considerable maintenance and are nonetheless subject to failure.
Accordingly, it is a general object of the present invention to eliminate the use of a regulating valve in a liquid rheostat by providing a variable speed electric motor for driving the circulating pump which circulates electrolyte solution from the reservoir to the electrode compartment. By varying the speed of the electric motor, the electrolyte solution level in the electrode compartment may be selectively regulated in order to control the operating speed of the motor which drives the primary pump used in pumping liquid from the well. Use of a regulating valve to meter flow from the electrode compartment to the reservoir is unnecessary.
Another object of the present invention is to provide a circulating pump driven by a variable speed electric motor which is controlled by a sensor immersed in the well. More specifically, it is an object to provide a sensor which will produce an electrical signal to a motor control indicative of the amount of liquid in the well. The motor control then directly regulates the speed of the variable speed electric motor driving the circulating pump.
It is another object of the present invention to provide a unitary cabinet assembly mounted above the primary pump. The cabinet assembly houses the liquid rheostat, including the electrode compartment, reservoir, the circulating pump and its variable speed electric motor together with the motor control.
These and additional objects and advantages of the present invention will be appreciated from a consideration of the drawings and the following detailed description of the preferred embodiment.